The next time she makes a comment about you having a baby and being unable to watch the children, call her bluff. "I'm sorry you feel that way. You are certainly entitled to your opinion and while I will miss taking care of *child*, you need to do what's best for your family. As I am finished for three weeks as of Thursday, I will forgo the *insert whatever your notice requirement is* notice period for ending care and will consider Thursday to be his last day. I'll be sure to have all of his things ready for you that day."

Otherwise, it's time to get firm. Let her know that if she needs to discuss anything with you regarding her sons care that she can call or text you between the hours of 1-3pm and that is it. You will not be responding to texts or messages outside of these hours. And then follow through.